Coating apparatus



Dec. 25, 1934. B, c, SKINNER COATING APPARATUS Filed Oct. 13. 1932ATTORNEYS Patented Dec. 25, 1934 UNITED STATES I COATING APP ARATUSBronson Cushing Skinne r, Dunedin, Fla.,'assignor to Brogdex Company,Winter Haven, Fla., a

corporation of Florida Application October 13,

7 Claims.

This invention relates to coating apparatus; and it relates moreparticularly to apparatus whereby globular objects, such as fresh fruit,may be provided with an extremely thin film-like protectivecoating, andmay also be given a lustrous glossy surface.

r In protectively coating certain articles, as in protectively coatingfresh fruit in preparation for market for example, the necessity arisesfor providing a special protective coating of such nature that it isfirmly adherent and relatively permanent in character but does not toocompletely seal the surface of the article; while at the same time thefinished coating must present exteriorly a pleasing luster or shinedemanded by the trade. The achievement of both these objectives in asingle coating step has been found to be impractical if not impossible.But by applying the coating in two successive steps, in the first ofwhich there is applied a suitably thin layer of a relatively softcoating material which will adhere tenaciously to the surface of thearticle, and in the second of which aharder coating material, capable ofimparting a satisfactory luster, is superimposed upon the layer ofsofter material in such manner as to minimize disturbance of suchunderlying layer, the problem may be satisfactorily solved. 'The presentinvention provides apparatus suitable for carrying out such a procedure,

The apparatus of the invention is of such character that the articles tobe treated may be provided initially with a'film coating of relativelysoft, low-melting protective material, applied most desirably bu t notnecessarily with the aid of heat and rubbing, afterwhich the, initiallycoated articles may then be exposed to contact with an air-suspension ofminute solid particles of a different coating material adapted tocomplete the 40 protective coating and give the articles the desiredfinal surface finish.

One desirable practical embodiment of the principles of the invention,as applied more particularly to apparatus for coating fresh fruit inpreparation for market, is illustrated in the accompanying drawingwherein Fig. 1 is a plan and Fig. 2 a side elevation, parts being brokenaway and in section to show details of construction.

Referring to the drawing, 11 indicates generally an applicator unit forapplying the initial filmlayer of coating material to the articles to becoated, such as oranges, grapefruit, apples or the like, for example.The articles may be continuously fed to the unit over delivery or chuteboard '10 by conveyor means 10. In this instance the 1932, Serial No.637,652

applicator unit comprises a plurality of cylindrical brush rolls 12rotatably mounted side by side in parallel, the members of each pair ofadjacent brush rolls cooperating to provide an elongated runwayextending lengthwise of the unit. These brush rolls may be rotatedcontinuously by any suitable driving means. The brush rolls are enclosedin a housing 13 providing a chamber in the lower part of which, belowthe brush rolls,- are suitable heating means 14, such as steam coils, bywhich the temperature within the chamber may be maintained substantiallyabove the melting point of the coating material to be applied in thisunit, The housing 13 is provided with entrance and exit openings eachguarded by 15 a flexible flap closure 13. At 15 is indicated generally adevice for atomizing or nebulizing molten coating material, arranged todischarge into the interior of the housing through pipe 16 and atomizingnozzles 17, which latter are adja- 20 cent the upper or intake ends ofthe polisher brush rolls. These brush rolls may slope gently toward theopposite or discharge end of the polisher or brush roll unit, asindicated. The atomizing unit 15 may be of any suitable type, oneparticularly suitable type being that disclosed in this applicants priorPatent No. 1,830,297 of November 3, 1931 which, however, is referred tohere merely by way of a desirable typical example. While means foratomizing the initially applied coating material on the fruit is mostdesirable, other types of applying means, not effecting atomization andnot necessarilyincluding heating means, may be employed within thebroader aspects of the invention. But the specific form of apparatushere illustrated affords particularly great advantages. As described inapplicant's prior patent aforesaid, the atomizing unit comprises acontainer in which solid coating material charged thereinto is melteddown and main- 40 tained molten by suitable heating means; saidcontainer, together with compressed air supply means, being so connectedto the atomizing nozzles that a regulable quantity of the molten coatingmaterial may be discharged therethrough un- 5 der pressure to form a fogor mist of said material.

At 18 is a roller belt conveyor arranged to receive the preliminarilycoated articles which leave unit 11 over chute board 11 and to carrythem into and through a chamber enclosed by a hood or housing 19 mountedjustabove the conveyor and extending across its entire width. This hoodhas entrance and exit openings, each covered by a flexible closure flap19*. Another atomizing or nebulizing unit 20, similar to unit 15 abovedescribed, is arranged to atomize molten coating material throughsuitable nozzle means 21'into the upper part of the chamber enclosed byhood 19 but, unlike chamber v13, chamber 19 is unheatedin order thatmolten coating material atomized thereinto may immediately solidify inthe form of very fine solid particles. A continuation or extension ofhead 19 is arranged below the conveyor 18, as indicated at 22, and isprovided with an outlet 23 connected to the intake of the suction fan orblower 24, which is arranged to discharge into a suitable dust separatordevice 25, such as a cloth bag.

.At 26 is a second rotary brush roll unit or polisher to which conveyor18 delivers articles over chute board 18 after they have passed throughthe chamber enclosed by the hood 19. This second polisher unit need notbe enclosed by a housing and is not provided with heating means. Itsbrush rolls 27 are mounted and arranged to be driven continuously in thesame manner as the brush rolls of the unit 11 already described.

In' operation, the articles to be coated, oranges for example, may bedelivered, as by roller belt conveyor 10, to the upper ends of therunways formed by brush rolls 12 of the first brush roll unit 11.Coating material, such as paraffin wax for example, suitable'for initialapplication to the articles, is melted in unit 15 and atomized ornebulized through spray nozzles 17 into the chamber enclosed by thehousing 13, which chamber may be heated by the steam coils 14 to atemperature sufiiciently above the melting point of the parafiin wax.The articles delivered to the unit 11 receive a small quantity of moltencoating material which is sprayed upon them through spray nozzles 17,and then continue to travel down the long runways between the polisherbrushes in the heated atmosphere, meanwhile being continuously subjectedto vigorous rubbing by the rapidly rotating brush rolls of horsehair orthe like. This ensures thorough and uniform spreading of the molten orsemi-molten coating material over the entire surface of the articles inavery thin film.

The articles provided with their initial protective coating anddischarged from unit 11 are received by roller conveyor 18 and arethereupon exposed to ordinary atmospheric temperature, with the resultthat the paraflin coating almost instantly sets or becomes solid,although it-does not at once attain its final hardness but remainsnoticeably tacky or sticky for a short time. In this condition thearticles are carried by the conveyor 18 into and through chamber 19where they encounter a cloud or air-suspension of minute solid dust-likeparticles of a coating material which is generally harder and highermelting than the coating material employed in the first coating unit 11.Ihis harder and higher melting coating material may be carnauba wax, ina typical instance, melted in unit 20v and atomized or nebulized therebythrough nozzle means 21 into the chamber 19. vThe atmosphere in chamber19 being at a temperature much below the melting point of the atomizedcoating material, the latter. immediately congeals or solidifies fromits molten condition. The resultant cloud or air-suspension of minutehard wax particles in solid form bathes the articles as they travelthrough the chamber and are slowly turned over and over by the action ofthe ing into the separator 25 a mixtureof air and excess of suspendedwax particles which latter collect in the separator and may be againused, if desired. The fan or blower thus acts to direct a systematictravel of the air-suspension downwardly through the chamber in contactwith the articles, and also ensures introduction of a con-, trollableamount of cooling air from outside whereby to prevent undue rise oftemperature in the chamber due to the continuous introduction ofnebulized hot molten wax thereinto. This provides'a convenient way ofkeeping the temperature in the chamber well below the melting point ofthe nebulized coating material and at the same time of preventingdissipation of excess of impalpably fine wax dust particles into thesurrounding atmosphere to the annoyance of the operators of theapparatus. I

Upon leaving the chamber 19, the articles with their adherent deposit ofsolid dust-like particles of the harder coating material pass down therunways of the brush roll polisher 26 which acts to thoroughly rub anddistribute said deposited coating material uniformly over the surface ofthe articles, this operation being conducted at ordinary atmospherictemperature. The brush rolls 2'7 of this polisher unit mayadvantageously be driven at a higher rate of speed than those ofpolisher unit 11 in order to exert an actual bufling efiect upon thesurface of the articles and develop a good luster or shine thereon. Forinstance, with a diameter of 7 inches, the brush rolls 27 mayadvantageously be driven at approximately 400 R.,P. M. to give a brushsurface speed of about 800 feet per minute. Under the conditionsdescribed, the action of the rapidly rotating cylindrical brushes uponthe dust-like deposit of the harder coating material, besides developing a fine luster, works the deposit into firm adherence with theunderlying thin layer of softer coating material, which remainspractically undisturbed and to which the finishing layer of hardermaterial adheres far more tenaciously than it would adhere directly tothe surface of the article.

As here illustrated, the roller conveyor 18 interposed between the twobrush roll units 11 and 26 is of such length that, in the usualoperation of the apparatus, the articles being coated are exposed toatmospheric temperature for a short period of time, on the order of 15to 20 seconds,

for example, before entering chamber 19. This brush roll unit 26 toreceive the initially coated articles directly from unit 11, in whichcase the 1,985,848 chamber 19, 22, may be'arranged at the head orarticles and to coat them initially with suitably adherent coatingmaterial while directing them to a point of discharge, in combinationwith further applicator means arranged to receive continuously initiallycoated articles discharged from the first applicator means and'toprovide them with a coating of luster-imparting material while directingthe articles to a point of discharge, such further applicator meansincluding an unheated chamber, a container for coating material, meansfor heating said container to melt solid coating material chargedthereinto, and compressed air supply means, together with atomizingnozzle means connected to said container and compressed air supply meansand arranged to discharge into said unheated chamber, thereby to producea cloud or air-suspension of fine solid particles of said coatingmaterial in the path of travel of said articles, and rubbing meansarranged to act on the articles upon which such solid particles aredeposited.

2. Coating apparatus comprising a rotary brush roll unit, a housingenclosing the same, means for feeding articles to said brush roll unit,a device adapted and arranged to melt solid coating material and toatomize the molten coating material into contact with articles fed tosuch brush roll unit, and heating means adapted and arranged to maintainthe temperature within said housing above the melting point of parafiinwax, in combination with a second rotary brush roll unit, means fortransferring articles thereto from the first brush roll unit, and adevice adapted and arranged to melt solid coating material and toatomize the molten coating material into the path of travel of sucharticles between the point where they leave the first brush roll unitand the point where they leave the second, such path being exposedtoatmospheric cooling sufflcient to ensure solidification of such atomizedmolten coating material before it gmtacts said articles. 3. Coatingapparatuscomprising means for applying hot molten butnormally solid waxyma-- terial to articles to be coated, rotary brush roll mechanismcooperating therewith to rub said material over thejsurface of thearticles, a housing enclosing said mechanism, and means for heating theinterior of said housing, to a temperature sufiicientto preventsolidification of said waxy material while it is, being rubbed on saidarticle, in combination with means adapted and arranged to produce frommolten waxy material an air suspension of fine solid waxy particles, inan unheated environment, a second rotary brush roll mechanismcooperating therewith, and located in said unheated environment, andmeans for transferring articles from the first mentioned" brush rollmechanism into contact with such suspension of solid wax particles andinto position to be acted upon by said second rotary brush roll mechanis4. Coating apparatus comprising two rotary brush roll units arranged inseries, a roller belt. conveyor interposed between them and arranged toreceive, articles discharged from the first and deliver-them to thesecond, coating material supply means and heating means cooperating withthe first rotary brush roll unit for applying coating material insubstantially-molten condition 'to articles, and means for contacting acloud or air-suspension of fine solid particles of coating material witharticles while they are on said conveyor, said conveyor being disposedin an environment cool enough to prevent melting of said solidparticles.

5. Coating apparatus as defined in claim 4, wherein a molten coatingmaterial atomizer is provided to produce the said air-suspension, and anexhausting device directs the same into the path'of travel of thearticles on said conveyor.

6. Coating apparatus comprising two rubbing units arranged'to actsuccessively on articles to be coated, means for driving said unitscontinuously to effect travel of articles through them in a definitepath, separate coating material supply devices cooperating with therespective rubbing units in the application of coating ma--' articletravel into which said atomizing means discharges.

7. Coating apparatus comprising applicator means operable to coatglobular articles initially with suitably adherent coating materialsolid at ordinary atmospheric temperatures, in combination with furtherapplicator means operable to provide the initially coated articles witha further coating Minster-imparting material, such further applicatormeans including anatomi'zing or nebulizing device operable to provide asupply of such luster-imparting material in hot molten condition and toproduce therefrom a cloud or air-suspension of fine solid particles ofsaid coating material in an unheated path of travel of said articles, ahousing forming a chamber within whichthe cloud or suspension of solidparticles is confined, and rubbing means arranged in said unheated pathto act on the articles upon which

